It is well known that, with the rapid development of the Internet, it has become popular to post various images, captured by using cameras and/or edited by using personal terminals such as personal computers, on Internet forums, homepages and blogs.
In this case, images produced by an individual may be copied illegally to be posted at other places or to be used for purposes other than originally intended ones.
To solve such problems, for example, watermarking method has been used to prevent illegal image copies. However, in this method, a watermark must be inserted into an image at the time that it is produced. Therefore, this method has drawbacks in that image copies become difficult to detect if someone deletes the watermark, and copied images become difficult to identify if someone deletes the watermark of the image and changes colors thereof or edits some portions thereof.
Further, regarding the identification of copied images from an original image, a thesis entitled “Suitability Test of MPEG-7 Visual Descriptors as an Identifier of Modified Images” (published on Feb. 3, 2006) is presented at FCV2006. This thesis discloses a method of identifying and inspecting copies of an original image based on a color distribution, a texture, an edge histogram and the like of the original image by using six descriptors (namely, scalable color descriptor, color layout descriptor, color structure descriptor, homogeneous texture descriptor, edge histogram descriptor and region based descriptor) that are supported by MPEG-7. However, it is still difficult to detect copies that are modified or edited from the original image by using the method disclosed in the above-mentioned thesis.
As a further example of the conventional art, Korean Patent Application No. 10-2000-063655 (entitled “System and Method for protecting Copyright and Preventing Infringement of Copyright on Internet,” which is filed on Oct. 28, 2000) discloses a method of protecting copyrights by preventing infringements on the Internet. In this method, a copyright search server, which includes a search agent; a query interface unit; a query processor; a search engine; a pattern analyzer; a token management unit; an audio; image signal pattern processor; a pattern matching unit; a storage management unit; a storage unit; a charge payment module; and a copyright search result storage unit, is constructed on the Internet or an intra-network. The copyright search server provides Internet search results in response to a query made by a copyright holder by comparing patterns of documents or moving images, and determines whether the copyright has been infringed to protect the copyright holder's interests by preventing illegal copies from being distributed without authorization. However, the above-described method is also of limited use in the identification and inspection of copies that are modified and edited from the original image.